Cystic fibrosis (CF) has many health consequences. A reduction in the ability to perform exercise in patients with CF is related to greater death rates, steeper decline in lung function, and more frequent lung infections. However, the physiological mechanisms for this reduced exercise capacity are unknown. The investigators laboratory recently published the first evidence of systemic vascular dysfunction in patients with CF. Therefore, it is reasonable to suspect that the blood vessels are involved with exercise intolerance in CF. This study will look at how 1) blood flow and 2) artery function contribute to exercise capacity in CF.

Following the acute study, patients will be instructed to take 20 mg of sildenafil, three times a day, for 4 weeks. Exercise capacity and endothelial function will be determined within 48 hours following the last dose.

Drug: Sub-Chronic (4 weeks) Sildenafil

Exercise capacity and vascular function will be assessed 4 weeks following 20 mg three times per day (TID) of sildenafil for four weeks

Other Names:

Viagra

Revatio

Detailed Description:

The most disturbing aspect of Cystic Fibrosis (CF) is the associated premature death. Low exercise capacity predicts death in patients with CF and is also associated with a steeper decline in lung function and more lung infections. A critical barrier to improving exercise tolerance in patients with CF is the investigators lack of knowledge regarding the different physiological mechanisms which contribute to their lower exercise capacity. We have compelling data to indicate that the blood vessels may contribute to the low exercise capacity in CF. The impact of this proof of concept investigation will test Phosphodiesterase Type 5 inhibitors (PDE5) inhibitors as a potential therapy in CF and will explore blood flow and endothelial function as potential mechanisms which contribute to exercise intolerance in CF. Improvements in exercise capacity will not only contribute to a better quality of live for patients with CF, it will also increase longevity in these patients.

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Please refer to this study by its ClinicalTrials.gov identifier: NCT02057458